It has long been known that when acid chloride is allowed to react in an aqueous, alkaline mixture with an alcohol, an ester is produced. This known reaction was first investigated and applied by Lossen as reported in Ann. Vol 161, 347 (1872) and 265, 129 (1891) and then by Baumann, Ber. 19 3218 (1886) and Schotten, Ber. 17 2544 (1884). The reaction has received great attention, particularly for the production of benzoyl oxybenzene sulfonate salts. A detailed investigation of what has become known as the "Schotten-Bauman reaction" was published by F. A. Menalda, Rec. Trav. Chim. 49, 967-995 (1930). In this definitive study of the Schotten-Bauman reaction the simultaneous reactions of hydrolysis and alcoholysis of the acid chloride were studied. Menalda reported the effect, in the Schotten-Baumann reaction, of temperature, the nature of the acid chloride, the concentration and nature of the alcohol and the concentration and nature of the alkali. From the results of his experiments, Menalda concluded as follows:
1. The reaction between an alcohol and an acid chloride in aqueous solution should be carried out at the lowest possible temperature, since this is most favorable for high yields of ester. The reaction mixture should be cooled during the reaction to prevent any rise in temperature due to the heat of the reaction. PA1 2. Since the concentrated alcoholic solutions afford higher yields of ester the immediate dilution of the solution with the entire amount of alkali necessary for the reaction is unwarranted, alkali and acid chloride should be added alternately in portions. PA1 3. The use of caustic potash rather than caustic soda is to be recommended, since potassium hydroxide affords better yields of este than sodium hydroxide. PA1 (a) reacting, in an aqueous alkaline medium, an alcohol with a molar excess of an acid chloride with continuous moderate shearing agitation of the reaction mixture, whereby esters are formed, and PA1 (b) separating the granular ester from the reaction mixture.
Various uses of benzoyl oxybenzene sulfonate salts have been found through the years and a typical utility is reported in U.S. Pat. No. 4,535,108 to Rosenquist et al. According to this patent, the above-mentioned salts are useful as fire retardants in polycarbonates, said utility overcoming the shortcomings of previously employed fire retardants.
With popularization of use of the above-mentioned salts, the Schotten-Baumann reaction was further refined as reported in U.S. Pat. No. 4,908,474 to Sankey et al. A thorough review of the voluminous prior art relating to the Schotten-Bauman reaction is provided in said patent. The Schotten-Baumann reaction is disclosed by Sankey et al to be more efficient when the reaction is conducted with at least equal molar amounts of benzoyl chloride and an alkali metal phenyl sulfonate salt in the presence of a restricted amount of water and base and preferably in the presence of a molar excess of benzoyl chloride. It is further disclosed by Sankey et al that control of the benzoic acid residue in the benzoyl oxybenzene sulfonate salt is achieved by incorporating a small but effective amount of surfactant in the reaction medium.
As was noted by Sankey et al., benzoyl oxybenzene sulfonate salts have received renewed interest in industry because they are useful in bleaching systems. Such systems are most pertinent to the detergent industry and when employed in such industry large amounts of the salt are required. It is therefore desirable to efficiently produce large amounts of benzoyl oxybenzene sulfonate salts with a minimum of need for treatment of waste products. Typically, the prior art processes provided benzoyl oxybenzene sulfonate salts in the form of a fine powder which could then be processed, in a second step, into a granular form more suitable for detergent formulations. Typically, binder materials are employed to provide the granular product. A typical example of preparing granular detergent compositions is described in EPO 0 390 251 to Bortolotti et al. A series of steps with high speed and moderate speed granulators is described therein including the use of typical polymers as binder material to convert powder material into the granular form.
Because of the need to reduce undesirable waste products it is important to provide alternative methods which obviate the need for introducing organic materials and to efficiently produce benzoyl oxybenzene sulfonate salts in granular form and in large volume.